The purpose of this study was to characterize changes in gene expression in the brain of a seasonal hibernator, the goldenmantled ground squirrel, Spermophilus lateralis, during the hibernation season. Very little information is available on molecular changes that correlate with hibernation state, and what has been done focused mainly on seasonal changes in peripheral tissues. We produced over 4000 reverse transcription-PCR products from euthermic and hibernating brain and compared them using differential display. Twenty-nine of the most promising were examined by Northern analysis. Although some small differences were observed across hibernation states, none of the 29 had significant changes. However, a more direct approach, investigating expression of putative hibernationresponsive genes by Northern analysis, revealed an increase in expression of transcription factors c-fos, junB, and c-Jun, but not junD, commencing during late torpor and peaking during the arousal phase of individual hibernation bouts. In contrast, prostaglandin D2 synthase declined during late torpor and arousal but returned to a high level on return to euthermia. Other genes that have putative roles in mammalian sleep or specific brain functions, including somatostatin, enkephalin, growth-associated protein 43, glutamate acid decarboxylases 65/67, histidine decarboxylase, and a sleep-related transcript SD464 did not change significantly during individual hibernation bouts. We also observed no decline in total RNA or total mRNA during torpor; such a decline had been previously hypothesized. Therefore, it appears that the dramatic changes in body temperature and other physiological variables that accompany hibernation involve only modest reprogramming of gene expression or steady-state mRNA levels.

␤-Amyloid protein (␤AP) deposition is a neuropathologic hallmark of Alzheimer's disease (AD). Yet, the source of cerebral ␤AP in AD is controversial. We examined the production of ␤AP by the BV-2 immortalized microglial cell line using a sensitive enzyme immunoassay. Constitutive production of ␤AP was detected in conditioned media from unstimulated BV-2 cells. Further, production of ␤AP was induced by treatment of cultures by lipopolysaccharide (LPS) or ␤AP-(25-35) and was inhibited by the calpain protease inhibitor MDL 28170. Treatment of BV-2 cells with LPS or ␤AP-(25-35) did not affect cell-associated ␤-amyloid precursor protein levels. These findings suggest that microglia may be an important source of ␤AP in AD, and that microglial production of ␤AP may be augmented by proinflammatory stimuli or by ␤AP itself. Alzheimer's disease (AD)1 is a progressive neurodegenerative disorder characterized clinically by loss of cognitive function and neuropathologically by neuritic plaques. ␤-Amyloid protein (␤AP), the major extracellular protein constituent of AD plaques, consists of 39 -43 residues derived from a larger ␤-amyloid precursor protein (␤APP). The cellular source of the ␤AP deposits in AD brain is controversial (1-3). ␤APP is a ubiquitously expressed protein, present in multiple central nervous system cell types, including neurons, glia, and endothelial cells, as well as in other tissues of the body (4, 5). ␤AP itself is generated in small amounts by a wide variety of cell types and is normally found in biological fluids (6 -9), but in AD there is either increased production or decreased clearance of ␤AP, or both (10). Transgenic mouse models demonstrate that neuronal overexpression of ␤APP in abnormal isoform ratios and/or of mutant ␤APP is sufficient to result in cerebral ␤AP deposits (11,12). Yet, in AD there may be multiple cellular ␤AP sources which contribute to the total cerebral ␤AP burden.Activated microglia, which are found in and around ␤AP-containing neuritic plaques in AD brain, are candidates for ␤AP generating or processing cells (13-16). In addition, the association of activated microglia with the early stages of ␤AP deposition in diffuse plaques has been demonstrated (14). Microglia are important in cerebral cytokine production, antigen presentation, and release of cytotoxic compounds and, hence, are key components in the central nervous system immune response (17). Activation of microglia in AD is part of the low-level inflammatory reaction found in the vicinity of ␤AP-containing plaques. Although microglia have been shown to express ␤APP and its encoding mRNA both in vitro and in AD brain (18 -20), secretion of ␤AP by microglia has not been demonstrated previously.In vitro treatment of microglia with ␤AP or ␤AP fragments results in activation of the microglia and the release of inflammatory cytokines and reactive nitrogen intermediates (21,22). Recently, it has been shown that ␤AP induces its own production by smooth muscle cells (23). We treated the BV-2 immortalized murine microglial ce...

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